Dopamine D 1 and D 2 receptor distributions were studied in the brain of the mouse, rat, guinea pig, cat and monkey by means of in vitro quantitative autoradiography using [3H]SCH 23390 and [3H]CV 205-502 to label D 1 and D 2 subtypes respectively. The distribution of both subtypes of receptors was similar within the basal ganglia of all species investigated. The highest densities for both subtypes were found in the nucleus caudatus, putamen, nucleus accumbens, olfactory tubercle and substantia nigra. Outside of the basal ganglia, differences in the distribution of both receptors were found among the species examined in regions such as cerebellum, cortex, hippocampus, superior colliculus and olfactory bulb. In all species D 1 receptor densities were higher than those of D 2. The absolute amount of both subtypes, however, varied among species. These results indicate that dopamine receptor distribution is well preserved in the basal ganglia during evolution, although differences among species exist in their distribution outside the basal ganglia and their absolute amount.